Climate Change: Global Temperatures Still Above Average

Some skeptics have seized on a recent article in The Economist noting an apparent “hiatus” in global warming to argue that climate change is a fiction and efforts to address it are misguided. Those interpretations, which were voiced by some representatives at a recent House hearing on climate science, misrepresent both the article and the science it examines.

So what are the facts?

Zooming in on one day, one year or even one decade misses the larger picture emerging over the last century – that the concentration of greenhouse gases in the atmosphere is increasing and that average global temperatures have been rising. As a result, sea level is higher and climate scientists tell us to expect increasingly more frequent heat waves and heavy rainfall events. These changes can contribute to more frequent and severe flooding, more intense droughts, and more widespread wildfires.

The Economist article notes that over the past 15 years, air temperatures at the Earth’s surface have been flat. Although this is true, temperatures are still significantly higher than they were 30, 50, or 100 years ago – almost 1 degree Celsius above average temperatures in the first decade of the last century. And all the years in the 21st century (2001-2012) rank in the top 14 warmest of the 133-year instrumental record (See figure).

Throughout this warming trend, there have been ups and downs and, yes, flat periods, reflecting a host of factors, including volcanic eruptions and the movement of heat between the atmosphere and the ocean. As noted by the Economist, these factors may at times mask or undercut the effect of global warming; at other times, they may enhance it.

In particular, several recent studies (here, here, and here) suggest that the lack of recent warming is consistent with an increase in heat uptake by the oceans. In other words, the oceans are absorbing more of the excess heat in our atmosphere. Although the precise roles of the upper and deep ocean are still active research questions, these findings demonstrate that a “warming hiatus” in air temperatures does not suggest that global warming has stopped.

One issue that pervades the article: a mistranslation of the concept of “climate sensitivity,” which represents the amount of warming expected to occur if the concentration of carbon dioxide in the atmosphere doubles. It’s an estimate for long-term “equilibration” of the climate system, which is reached after many centuries. The article incorrectly interprets “sensitivity” as a prediction for global temperature on an annual or decadal timescale.

The bottom line is that greenhouse gases continue to accumulate in the atmosphere, raising global mean temperature and altering many weather patterns. Communities and businesses are already experiencing significant and costly impacts, which are likely to continue, absent significant steps to mitigate these emissions or adapt to the new and changing climate conditions.

Figure 1: Global temperature from 1950-2102 show significant warming occurring in the past 50 years. El Niño years, which favor warmer global temperatures, and La Niña years, which have historically been associated with relatively cooler global temperatures, are shown in color. Source: NOAA National Climate Data Center.

Dr. Joe Casola serves as Staff Scientist and Program Director for Science and Impacts at the Center for Climate and Energy Solutions. He oversees C2ES’s efforts to assess and communicate the current state of knowledge regarding climate change and its associated impacts, and to promote actions that strengthen climate resilience.

The charted temperature increases shown is for the time period of a positive Pacific Decadal Oscillation (PDO). So, naturally, the temperatures have risen. The last two centuries have shown global temperature increases of around 0.5 deg C (~ 0.9 deg F) per century. This is the pace for coming out of the LIA. The slowly rising CO2 levels show no "modulating" effect on global temps. That is, rapid changes in global temps do not correspond to a matched changes in CO2. Also, there is a misunderstanding of the GHE. We all think the Earth is 33 deg warmer due to the GHE. However, on the moon, with no atmosphere, the daylight temps are scortchingly high. Earth would fry without an atmosphere. So, does our atmosphere actually keep us from frying?

Given that the recent temperature increases started around 1910, well before significant anthropogenic emissions, I can't see how CO2 is blamed for this increase. Also, the rate of increase over the following 30 years was much the same as 1970 - 2000. How, then, can this be evidence that CO2 is a major contributor. If anything, it surely indicates that CO2, if anything, is probably a minor contributor.

If I look at temperatures for the past 2,000 and 5,000 years, and predict what should be happening now, I'd expect a temperature increase for the past century as we come out of the Little Ica Age. In other words, temperatures are doing exactly what history tells us they should be doing. Why is it suddenly CO2?

You ask why the Ice Age happened - is it coincidence that the Little Ice Age corresponded to the Maunder period?

But didn't the Global Warming advocates say it was going to get warmer "every" year? Can you provide a tempurature chart from the last ice age till now....I just want to see if it is warmer now that the last ice age and did the tempurature go up from then? Do we know why the last Ice Age happened. I am all for lowering resource usage and a better environment. But somehow a lot of the Global Warming mission appears to be about paying various enthusists money to try various gizmos that they make lots of money off of? The only 100% available power source with ZERO Co2 emission is nuclear. BIOMASS is basically a fraud where more CO2 is emitted into the air...while said BIOMASS promoters make money. Please explain the linkage between advocates making lots of money and poor solutions...off the back of this "crisis".

To answer your initial question, global warming advocates do not claim that each and every year will be warmer, though deniers do often raise such a bogus claim about advocates-of which you are an example